Topical fluorides have been the mainstay in the prevention of dental caries for decades. However, topical fluoride alone is not enough to thwart tooth decay in high-risk populations. The purpose of this Phase I application is to determine the technical and scientific feasibility of using a combination povidone-iodine (PVP-I)-5% sodium fluoride (NaF) varnish as a potential commercial product to prevent dental caries. The research will be conducted by the small business firm ADP Silver Dental Arrest, LLC, in collaboration with experienced researchers at the University of Washington Northwest Center to Reduce Oral Health Disparities. The Premier Dental Products Company will prepare the varnish to the specifications of the applicant at no cost to the grant. The Specific Aims of this Phase I SBIR are to: (1) Demonstrate that a new povidone iodine-sodium fluoride varnish has antimicrobial activity and fluoride bioavailability and enamel remineralization ability. (a) Use the in vitro moel developed by Castillo and colleagues to determine the bioavailability of fluoride and iodine release from an experimental povidone-iodine- sodium fluoride varnish; (b) Use an in vitro model of Tanzer and colleagues to assess the additive (indifferent), potentially synergistic, or potentially antagonistic effects of sodium fluoride and povidone-iodine against Streptococcus mutans using the criteria of Eliopoulos and Moellering; (c) Use a slight modification the Featherstone laboratory pH cycling model to test remineralization. (2) Assess the esthetic and organoleptic properties of the new povidone iodine-sodium fluoride varnish. Caries researchers for sometime have suggested strategies that combine an antiseptic with topical fluoride to reduce or eliminate the oral cariogenic bacteria reservoir in addition to topical fluoride which primarily remineralizes teeth enamel. Povidone-iodine is an FDA-approved and widely used bactericidal antiseptic. For the oral flora, iodine has preferential activities against streptococcl species. Moreover, iodine's effectiveness may last as long as six months.